SCSNSCSN http://www.scsn.org Southern California Seismic Network Mon, 21 May 2018 18:34:27 +0000 en-US hourly 1 https://wordpress.org/?v=4.9.2 05/08/2018, M4.5 near Cabazon ../../index.php/2018/05/08/05-08-2018-m4-5-near-cabazon/ ../../index.php/2018/05/08/05-08-2018-m4-5-near-cabazon/#respond Tue, 08 May 2018 13:57:59 +0000 http://www.scsn.org/?p=2711 ]]> A M4.5 earthquake occurred at 4:49 local time this morning (May 8) under the San Bernardino Mountains, near a complex part of the San Andreas fault. Seismologists call this region the “San Gorgonio knot” because so many small faults intersect here and the main San Andreas trace is not clearly defined.

Historically, this area around Mt. San Gorgonio is the only part of the southern San Andreas fault that produces smaller quakes. Many M3-4 earthquakes have been recorded here. The largest were the M6.0 Desert Hot Springs earthquake in 1948 about 30 miles to the east and the 1986 M5.9 North Palm Springs earthquake that was less than 10 miles east of today’s earthquake.

The focal mechanism calculated by Caltech and the USGS for this earthquake Moment Tensor Page shows the event happened on a fault that strikes a little north of east-west and that the motion was primarily thrust faulting. This means that the north side moved up and over the lower south side of the fault. This is very similar to the motion we saw in the 1986 North Palm Springs earthquake. (https://authors.library.caltech.edu/48710/.)

This morning’s M4.5 was felt from San Diego to Los Angeles. More than 10,000 people have reported feeling it at Did you feel it?. The strongest shaking recorded by the instruments is Intensity VI.

This size earthquake is common in California, happening many times each year somewhere in the state. This is normal activity and has no relationship to the Hawaii eruption.

Technical information about this earthquake and its aftershocks:

  • 08 May 2018 04:49:34 PDT, (34.017, -116.780), depth 12.9km, 11km N of Cabazon, California.
  • Aftershocks: so far (09 May 2018, 10:40AM PDT) there have been 88 aftershocks recorded, the largest M3.2 (smallest M0.2). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • Plot of seismicity through time, from 0.5 days before the M4.5 Cabazon event to approximately 1.25 days after. Top plot shows cumulative earthquake count against time. Bottom plot shows earthquake magnitude against time, the M4.5 event and M3.2 aftershock are plotted as red stars.
    Map showing the M4.5 earthquake near Cabazon (red star) with foreshocks and aftershocks in a 10km radius shown as circles colored by time (blue = early, red = late) and sized by magnitude. Grey stars labelled by magnitude show historic earthquakes. Grey lines show the mapped fault strands in the San Andreas fault zone.
  • Historical seismicity: since our records began in 1932 we’ve had 46 events of M4 or greater within 10km of today’s event, the largest was M6.0 (1986/07/08) and the most recent was M4.4 on 06 Jan 2016.
  • Nearby faults: San Andreas fault zone, San Bernardino Mountains section (3.0 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.

Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed.The closest station to the earthquake shown in the view is CI.WWC in Palm Springs at approximately 35km.

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05/01/2018, M3.7 near San Clemente Is ../../index.php/2018/05/01/05-01-2018-m3-7-near-san-clemente-is/ ../../index.php/2018/05/01/05-01-2018-m3-7-near-san-clemente-is/#respond Tue, 01 May 2018 11:48:01 +0000 http://www.scsn.org/?p=2703 ]]>
  • 01 May 2018 04:22:22 PDT, (32.787, -118.443), depth 8.0km, 10km WSW of San Clemente Is.
  • Aftershocks: so far (01 May 2018, 07:20AM PDT) there have been 3 aftershocks recorded, the largest M3.4 (smallest M2.8). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • Historical seismicity: since our records began in 1932 we’ve had 4 events of M4 or greater within 10km of today’s event, the largest was M5.8 (1951/12/26) and the most recent was M4.2 on 16 Aug 2001.
  • Nearby faults: San Clemente fault zone (San Clemente fault) (11.0 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Li
    ve Seismograms Feed.The closest station to the earthquake shown in the view is CI.RPV in Long Beach at approximately 106km.

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    04/25/2018, M3.9 near Borrego Springs ../../index.php/2018/04/26/04-25-2018-m3-9-near-borrego-springs/ ../../index.php/2018/04/26/04-25-2018-m3-9-near-borrego-springs/#respond Thu, 26 Apr 2018 01:44:49 +0000 http://www.scsn.org/?p=2695 ]]>
  • 25 Apr 2018 18:36:00 PDT, (33.380, -116.298), depth 13.9km, 16km NNE of Borrego Springs, California
  • Aftershocks: so far (26 Apr 2018, 02:27PM PDT) there have been 5 aftershocks recorded, the largest M1.2 (smallest M0.8). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • There were 4 events during the 3 days prior to the earthquake (within a 10 km radius), the largest was M2.5 (2018/04/25).
  • Historical seismicity: since our records began in 1932 we’ve had 41 events of M4 or greater within 10km of today’s event, the largest was M6.0 (1937/03/25) and the most recent was M5.2 on 10 Jun 2016.
  • Nearby faults: San Jacinto fault zone, Anza section (Clark fault) (1.1 km), San Jacinto fault zone, Anza section (5.8 km), San Jacinto fault zone, Coyote Creek section (6.6 km), San Jacinto fault zone, Coyote Creek section (Coyote Creek fault) (6.8 km) and San Jacinto fault zone, Anza section (Buck Ridge fault) (7.0 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station to the earthquake shown in the view is CI.WWC in Palm Springs at approximately 60km.

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    04/22/2018, M3.9 near Thousand Palms ../../index.php/2018/04/23/04-22-2018-m3-9-near-thousand-palms/ ../../index.php/2018/04/23/04-22-2018-m3-9-near-thousand-palms/#respond Mon, 23 Apr 2018 01:03:09 +0000 http://www.scsn.org/?p=2683 ]]>
  • 22 Apr 2018 17:46:08 PDT, (33.922, -116.322), depth 8.2km, 13km NNE of Thousand Palms, California
  • Aftershocks: so far (23 Apr 2018, 07:19AM PDT) there have been 7 aftershocks recorded, the largest M2.2 (smallest M0.8). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • Historical seismicity: since our records began in 1932 we’ve had 85 events of M4 or greater within 10km of today’s event, the largest was M6.1 (1992/04/23) – the Joshua Tree earthquake. The most recent event was M4.0 on 06 Aug 2010.
  • Nearby faults: unnamed Fault in the Little San Bernardino Mountains (1.1 km), Blue Cut fault zone (Blue Cut fault) (2.0 km), Eureka Peak fault (5.4 km), San Andreas fault zone, San Bernardino Mountains section (North Branch SAF) (6.3 km), San Andreas fault zone, San Bernardino Mountains section (6.8 km), Burnt Mountain fault zone (East Wide Canyon fault) (7.1 km), Indio Hills fault zone (8.9 km), San Andreas fault zone, San Bernardino Mountains section (South Branch SAF) (9.3 km) and Long Canyon fault (11.1 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed.

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    04/16/2018, M3.8 near Grapevine ../../index.php/2018/04/16/04-16-2018-m3-8-near-grapevine/ ../../index.php/2018/04/16/04-16-2018-m3-8-near-grapevine/#respond Mon, 16 Apr 2018 17:11:12 +0000 http://www.scsn.org/?p=2675 ]]>
  • 16 Apr 2018 09:36:48 PDT, (35.043, -119.042), depth 7.7km, 15km NW of Grapevine, California.
  • Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. The following probability report is based on the statistics of aftershocks typical for California. This is not an exact prediction, but only a rough guide to expected aftershock activity. This probability report may be revised as more information becomes available.
    • STRONG AFTERSHOCKS (Magnitude 5 and larger): at this time (immediately after the mainshock) the probability of a strong and possibly damaging aftershock IN THE NEXT 7 DAYS is less than 10%
    • EARTHQUAKES LARGER THAN THE MAINSHOCK: most likely, the recent mainshock will be the largest in the sequence. However, there is a small chance (APPROXIMATELY 5% TO 10%) of an earthquake equal to or larger than this mainshock in the next 7 days.
    • WEAK AFTERSHOCKS (Magnitude 3 to 5): in addition, up to approximately 2 SMALL AFTERSHOCKS are expected in the same 7-DAY PERIOD and may be felt locally.
  • Historical seismicity: since our records began in 1932 we’ve had 103 events of M4 or greater within 10km of today’s event, the largest was M7.5 (1952/07/21) and the most recent was M4.2 on 22 Sep 2005. Known as the Kern County earthquake, the Mw7.5 event on July 21, 1952 caused widespread damage and was felt across California and Nevada. See the special report on the SCEDC website for more information. Many of the other catalog events in this area are aftershocks of the 1952 Kern County earthquake. The M3.7 earthquake near Bodfish on April 13, 2018, was located approximately 60 km from this event near Grapevine, but is also along the section of fault responsible for the Kern County earthquake.
  • Nearby faults: Wheeler Ridge fault zone (Wheeler Ridge fault) (1.5 km), Pleito fault zone, western Pleito section (Pleito fault) (3.8 km), unnamed faults (1952 earthquake fractures) (4.2 km), Pleito fault zone, eastern Pleito section (Pleito fault) (5.9 km) and Pleito fault zone, western Pleito section (Oak Hill thrust) (13.5 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed.

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    04/13/2018, M3.7 near Bodfish ../../index.php/2018/04/13/04-13-2018-m3-7-near-bodfish/ ../../index.php/2018/04/13/04-13-2018-m3-7-near-bodfish/#respond Fri, 13 Apr 2018 16:09:30 +0000 http://www.scsn.org/?p=2666 ]]>
  • 13 Apr 2018 08:24:46 PDT, (35.392, -118.545), depth 4.8km, 22km SSW of Bodfish, California
  • Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • Nearby faults: White Wolf fault zone (White Wolf fault) (10.3 km) and Edison fault (13.4 km). The White Wolf fault was the site of the largest earthquake in southern California since the Fort Tejon event of 1857. Known as the Kern County earthquake, this Mw7.5 event on July 21, 1952 caused widespread damage and was felt across California and Nevada. See the special report on the SCEDC website for more information.
  • Historical seismicity: since our records began in 1932 we’ve had 90 events of M4 or greater within 10km of today’s event, the largest was M5.6 (1952/07/31) and the most recent was M4.2 on 19 Apr 2014. Many of these events are aftershocks of the 1952 Kern County earthquake.
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station to the event shown is Bakersfield (BAK) at 50km.

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    04/05/2018, M5.3 near Santa Cruz Is ../../index.php/2018/04/05/04-05-2018-m5-3-near-santa-cruz-is/ ../../index.php/2018/04/05/04-05-2018-m5-3-near-santa-cruz-is/#respond Thu, 05 Apr 2018 20:19:32 +0000 http://www.scsn.org/?p=2657 ]]>
  • 05 Apr 2018 12:29:16 PDT, (33.837, -119.725), depth 9.9km, 29km SW of Santa Cruz Is.
  • Foreshocks:No earthquakes were detected within 20 km of this earthquake in the preceding week. This is not unusual and is a reminder that earthquakes often occur without any previous short-term seismic activity.
  • Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • The earthquake occurred on an offshore strike-slip fault; further analysis will be needed to identify the fault or fault system with which it is associated. An earthquake of this size is not necessarily associated with a major, named fault. Nearby faults: Santa Cruz Island fault (14.2 km). The strike slip mechanism is shown below.
    Moment tensor solution for the 05 Apr 2018 earthquake near Santa Cruz Is.

  • Historic seismicity: two earthquakes with magnitudes of 4-5 have occurred in the general region since 1940 (M4.8 in 1954/08/26 and M4.1 2005/07/24). On December 21, 1812, a large earthquake struck in the Santa Barbara Channel, generating a tsunami that carried a ship inland. This earthquake is poorly understood due to its timing, but illustrates that offshore faults are capable of hosting earthquakes with magnitudes upwards of 7. On June 29, 1925, a magnitude 6.6 earthquake occurred offshore of Santa Barbara.
  • The earthquake was widely felt along the California coast as shown in the felt report plot below. Anything more than light shaking would only be expected on the channel islands, close to the epicenter.

    Instrumental shaking is shown in the ShakeMap below.

  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest station to the epicenter represented below is CI.LCP in Santa Maria, at a distance of 112 km from the event. The furthest station shown is CI.MLAC in Mammoth Lakes, over 400 km away. With an event of this magnitude, and the sensitivity of our seismic instruments, we detect this earthquake across our entire seismic network.

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    03/07/2018, M3.7 near Simmler ../../index.php/2018/03/07/03-07-2018-m3-7-near-simmler/ ../../index.php/2018/03/07/03-07-2018-m3-7-near-simmler/#respond Wed, 07 Mar 2018 18:43:19 +0000 http://www.scsn.org/?p=2618 ]]>
  • 07 Mar 2018 10:05:00 PST, (35.485, -120.027), depth 8.5km, 15km N of Simmler, California
  • Aftershocks: so far there have been no aftershocks recorded. Some may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%%) that a larger quake could occur, with the likelihood decreasing over time.
  • Nearby faults: San Andreas fault zone, Cholame-Carrizo section (0.6 km), San Juan fault zone (12.7 km) and San Juan fault zone (San Juan fault) (13.9 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed.The closest station to the epicenter represented below is CI.SMR at 54km away

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    02/26/2018, M3.7 near Anza ../../index.php/2018/02/26/02-26-2018-m3-8-near-anza/ ../../index.php/2018/02/26/02-26-2018-m3-8-near-anza/#respond Mon, 26 Feb 2018 18:55:08 +0000 http://www.scsn.org/?p=2604 ]]>
  • 26 Feb 2018 10:44:41 PST, (33.483, -116.503), depth 12.6km, 18km ESE of Anza, California
  • Aftershocks: so far (28 Feb 2018, 08:47AM PST) there have been 17 aftershocks recorded, the largest M1.9 (smallest M0.5). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • There were 25 events during the 3 days prior to the earthquake (within a 10 km radius), the largest was M1.5 (2018/02/23).
  • Historical seismicity: since our records began in 1932 we’ve had 26 events of M4 or greater within 10km of today’s event, the largest was M5.6 (2005/06/12) and the most recent was M5.2 on 10 Jun 2016.
  • Nearby faults: San Jacinto fault zone, Anza section (Clark fault) (0.2 km), San Jacinto fault zone, Anza section (1.6 km), San Jacinto fault zone, Coyote Creek section (Coyote Creek fault) (3.1 km), San Jacinto fault zone, Anza section (Buck Ridge fault) (3.1 km) and San Jacinto fault zone, Coyote Creek section (6.0 km).
  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed. The closest stations represented in the feed below are CI.WWC and CI.HMT2 at 51.7km and 52.5km away from the epicenter respectively.

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    01/25/2018, M4.0 near Trabuco Canyon ../../index.php/2018/01/25/01-25-2018-m4-0-near-trabuco-canyon/ ../../index.php/2018/01/25/01-25-2018-m4-0-near-trabuco-canyon/#respond Thu, 25 Jan 2018 14:54:35 +0000 http://www.scsn.org/?p=2560 ]]>
  • 25 Jan 2018 02:09:56 PST, (33.742, -117.492), depth 11.2km, 12km NE of Trabuco Canyon, California
  • Aftershocks: so far (29 Jan 2018, 08:12AM PST) there have been 27 aftershocks recorded, the largest M3.1 (smallest M0.3). More may be expected in the next few days, the largest expected is approximately 1 magnitude unit smaller than the mainshock. There is a small chance (about 5%) that a larger quake could occur, with the likelihood decreasing over time.
  • There was 1 event during the 3 days prior to the earthquake (within a 10 km radius), with M1.2 (2018/01/22).
  • Plot of seismicity through time, from 3 days before the M4.0 Trabuco Canyon event to approximately 3.5 days after. Top plot shows cumulative earthquake count against time. Bottom plot shows earthquake magnitude against time, the M4.0 event and M3.1 aftershock are plotted as red stars.

  • Historical seismicity: since our records began in 1932 we’ve had 7 events of M4 or greater within 10km of today’s event, the largest was M5.2 (1938/05/31) and the most recent was M4.7 on 02 Sep 2007.
  • Map showing the M4.0 earthquake near Trabuco Canyon (red star) with foreshocks and aftershocks in a 10km radius shown as circles colored by time (blue = early, red = late) and sized by magnitude. Grey stars labelled by magnitude show historic earthquakes. Grey lines show the mapped fault strands in the Elsinore fault zone.

  • Mechanism: the event has a thrust mechanism on a near east-west trending fault plane as shown by the moment tensor below.
    Moment tensor for the M4.0 event on 25 Jan 2018 near Trabuco Canyon.

    The nearest mapped faults to this event are in the Elsinore fault zone, most strands of which usually host strike-slip events. However, the Glen Ivy strands of the Elsinore fault show oblique as well as strike-slip mechanisms (as shown below), and in the region north of Lake Elsinore it is thought the fault may form a restraining bend at depth contributing to uplift of the Santa Ana mountains (Hull & Nicholson, 1992) and consistent with thrust mechanisms such as the 2018/01/25 earthquake.

    Figure from Hull & Nicholson (1992) showing focal mechanisms for selected earthquakes from the Elsinore-Temecula trough. The M4.0 event on 25 Jan 2018 near Trabuco Canyon has been added as a red star, and shows a consistent mechanism with earlier observed earthquakes.

  • Nearby faults: Elsinore fault zone, Glen Ivy section (Glen Ivy South fault) (0.9 km), Elsinore fault zone, Glen Ivy section (Glen Ivy North fault) (1.4 km), Elsinore fault zone, Temecula section (Willard fault) (2.0 km), Elsinore fault zone, Glen Ivy section (Eagle fault) (5.6 km), Elsinore fault zone, Glen Ivy section (Main Street fault) (10.7 km), Elsinore fault zone, Chino section (Chino fault) (12.8 km) and Elsinore fault zone, Temecula section (Wildomar fault) (13.1 km).
  • The ShakeMap (below) shows that ground shaking was strongest to the north and east of the earthquake hypocenter, consistent with stronger shaking being felt in basins and valleys (generally weaker geology, greater chance of amplification effects), and potentially also an effect of source mechanism.
    ShakeMap for the M4.0 event on 25 Jan 2018 near Trabuco Canyon.

  • Links for: USGS earthquake page, ShakeMap, DYFI, waveforms.
  • Visit our special reports page for further information on local notable earthquakes.
  • Below are the waveform data associated with this event, as recorded in our Live Seismograms Feed.

  • References:
    Hull, A.G. & C. Nicholson, 1992. Seismotectonics of the Northern Elsinore Fault Zone, Southern California. Bull. Seismo. Soc. Am. 82 (2) pp. 800-818.
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